Innervation zones location and optimal electrodes position of obliquus internus and obliquus externus abdominis muscles

The assessment of abdominal muscles has became popular in recent years because the study of “core muscles” is now considered a pivotal approach for a number of fields. The purpose of this study was to describe the innervation zone (IZ) locations and optimal electrode sites in two core muscles: the obliquus externus (OE) and the obliquus internus (OI) abdominis muscles. Twenty healthy male subjects were recruited and the IZ location was studied during a submaximal isometric contraction using multichannel surface EMG.The optimal electrode position for OI was found to be 2 cm lower the most prominent point of the anterior superior iliac spine, just medial and superior to the inguinal ligament. The optimal electrode position for OE was found to be 14 cm from the median line, lower the level of 1 cm above umbilicus, parallel to the line extending from the most inferior point of the costal margin to the opposite pubic tubercle (almost 45° with respect to the median line).Findings showed that for OI and OE muscles it is possible to provide indications for a muscle belly area suited for proper positioning of at least an electrode pair.     

Estimating the location and shape of hybrid zones

We propose a new model to make use of georeferenced genetic data for inferring the location and shape of a hybrid zone. The model output includes the posterior distribution of a parameter that quantifies the width of the hybrid zone. The model proposed is implemented in the GUI and command-line versions of the Geneland program versions ≥ 3.3.0. Information about the program can be found on http://www2.imm.dtu.dk/gigu/Geneland/.     

Site-directed mutagenesis of Escherichia coli 23 S ribosomal RNA at position 1067 within the GTP hydrolysis centre

Site-directed mutagenesis has been used to change, specifically, residue 1067 within 23 S ribosomal RNA of Escherichia coli. This nucleoside (adenosine in the wild-type sequence) lies within the GTPase centre of the larger ribosomal subunit and is normally the target for the methylase enzyme responsible for resistance to the antibiotic thiostrepton. The performance of the altered ribosomes was not impaired in cell-free protein synthesis nor in GTP hydrolysis assays (although the 3 mutant strains grew somewhat more slowly than wild-type) but their responses to thiostrepton did vary. Thus, ribosomes containing the A to C or A to U substitution at residue 1067 of 23 S rRNA were highly resistant to the drug, whereas the A to G substitution resulted in much lesser impairment of thiostrepton binding and the ribosomes remained substantially sensitive to the antibiotic. These data reinforce the hypothesis that thiostrepton binds to 23 S rRNA at a site that includes residue A1067. They also exclude any possibility that the insensitivity of eukaryotic ribosomes to the drug might be due solely to the substitution of G at the equivalent position within eukaryotic rRNA.     

Hip joint centre location: An ex vivo study

The human hip joint is normally represented as a spherical hinge and its centre of rotation is used to construct femoral anatomical axes and to calculate hip joint moments. The estimate of the hip joint centre (HJC) position using a functional approach is affected by stereophotogrammetric errors and soft tissue artefacts. The aims of this study were (1) to assess the accuracy with which the HJC position can be located using stereophotogrammetry and (2) to investigate the effects of hip motion amplitude on this accuracy. Experiments were conducted on four adult cadavers. Cortical pins, each equipped with a marker cluster, were implanted in the pelvis and femur, and eight skin markers were attached to the thigh. Recordings were made while an operator rotated the hip joint exploiting the widest possible range of motion. For HJC determination, a proximal and a distal thigh skin marker cluster and two recent analytical methods, the quartic sphere fit (QFS) method and the symmetrical centre of rotation estimation (SCoRE) method, were used. Results showed that, when only stereophotogrammetric errors were taken into account, the analytical methods performed equally well. In presence of soft tissue artefacts, HJC errors highly varied among subjects, methods, and skin marker clusters (between 1.4 and 38.5 mm). As expected, larger errors were found in the subject with larger soft tissue artefacts. The QFS method and the distal cluster performed generally better and showed a mean HJC location accuracy better than 10 mm over all subjects. The analysis on the effect of hip movement amplitude revealed that a reduction of the amplitude does not improve the HJC location accuracy despite a decrease of the artefact amplitude.     

Acoustic communication in a king penguin colony: importance of bird location within the colony and of the body position of the listener

This study focuses on the propagation of the display call used for individual recognition between penguin partners. Transmission of acoustic information in a noisy environment such as a king penguin colony is very difficult. Conditions of propagation were examined for two areas of the colony (hatching and courtship areas) and reception at three heights from the ground (10, 45 and 90 cm). Signal modification was assessed in terms of attenuation of signal, amplitude modulation and spectral content. The acoustic recognition of the mate, which is decisive for breeding success, took place in the hatching area where signal degradation was less great for all parameters studied. When the receiver was located 10 cm above the ground, degradation of the signal was much more pronounced than when it was located 45 or 90 cm above ground. The characteristic incubating attitude of the king penguin (i.e. standing with the head at 45 cm above the ground) enables it to receive the main part of the signal in spite of the noisy environment. Accepted: 19 October 1998     

Spatial compatibility and position of the effectors

Mean reaction times obtained with crossed hands (right had on the left and left hand on the right) are slower than reaction times obtained with uncrossed hands (right hand on the right and left hand on the left). These results have been explained as a compatibility effect between the responding hand and its spatial position. The goal of the present experiment was to establish whether the position of the hand is encoded by the subjects relative to their body (absolute position) or relative to the other hand (relative position). The subjects performed a discrimination task on two visual stimuli. Stimuli and hands were either on the same side of the body (both on the left or both on the right) or had different absolute position. In all conditions the subjects responded with crossed and uncrossed hands. The results support the hypothesis that relative position is encoded.     

Small cytoplasmic RNAs and their location within the cytoplasm

These studies were designed to establish the location of various species of small RNAs within the subcellular cytoplasmic compartments. Four cytoplasmic RNA-containing compartments were examined: (A) cytoskeleton-bound polyribosomal ribonucleoprotein (RNP) complexes, (B) soluble-phase polyribosomal RNP complexes, (C) cytoskeleton-bound free RNP complexes, (D) soluble-phase free RNP complexes. The presence of the small cytoplasmic RNA (scRNA) population and histone H4 and actin mRNAs in each compartment was examined to determine their spatial distribution within the cytoplasm. The 7S signal recognition RNA and the 5S and 5.8S rRNAs were distributed among all four compartments, while 4S tRNAs were localized largely in fraction D. Fraction C contained a group of seven abundant scRNAs, of approximately 105-348 nucleotides in length, which were localized almost entirely within the cytoskeleton-bound free RNP compartment. Actin mRNAs were localized in fraction A, the actively translating cytoskeleton-bound compartment. Actin mRNAs were localized in fraction A, the actively translating cytoskeleton-bound compartment. Following cytochalasin B treatment, actin mRNAs were released into the soluble phase, implicating a dependence on the integrity of actin filaments in its binding. Such treatment also released several of the scRNAs from their cytoskeleton-bound location. In contrast histone H4 mRNAs were much more widely dispersed, being present in all four cytoskeletal compartments. Approximately 60% of the H4 mRNAs, however, were localized within the soluble-phase polyribosomes in fraction B. Cytochalasin B treatment released only the small portion of untranslated histone H4 mRNA associated with the cytoskeleton in fraction C, suggesting that the binding of these H4 mRNAs was dependent in some manner upon the integrity of actin filaments.     

Microbial diversity within basement fluids of the sediment-buried Juan de Fuca Ridge flank

Despite its immense size, logistical and methodological constraints have largely limited microbiological investigations of the subseafloor basement biosphere. In this study, a unique sampling system was used to collect fluids from the subseafloor basaltic crust via a Circulation Obviation Retrofit Kit (CORK) observatory at Integrated Ocean Drilling Program borehole 1301A, located at a depth of 2667 m in the Pacific Ocean on the eastern flank of the Juan de Fuca Ridge. Here, a fluid delivery line directly accesses a 3.5 million years old basalt-hosted basement aquifer, overlaid by 262 m of sediment, which serves as a barrier to direct exchange with bottom seawater. At an average of 1.2 × 10⁴ cells ml⁻¹, microorganisms in borehole fluids were nearly an order of magnitude less abundant than in surrounding bottom seawater. Ribosomal RNA genes were characterized from basement fluids, providing the first snapshots of microbial community structure using a high-integrity fluid delivery line. Interestingly, microbial communities retrieved from different CORKs (1026B and 1301A) nearly a decade apart shared major community members, consistent with hydrogeological connectivity. However, over three sampling years, the dominant gene clone lineage changed from relatives of Candidatus Desulforudis audaxviator within the bacterial phylum Firmicutes in 2008 to the Miscellaneous Crenarchaeotic Group in 2009 and a lineage within the JTB35 group of Gammaproteobacteria in 2010, and statistically significant variation in microbial community structure was observed. The enumeration of different phylogenetic groups of cells within borehole 1301A fluids supported our observation that the deep subsurface microbial community was temporally dynamic.     

Dynamics of chromatin position within the interphase nucleus

In this article we attempt to analyze the relationship between the processes, which occur in the nucleus, and the dynamics of chromatin, as well as to classify the changes in the position of chromatin in the cell nucleus during the lifetime of the cell. The proposed concept integrates possible types of chromatin movement within the nucleus.     

Spatial variation in demography and population growth rate: the importance of natal location

1. Understanding the pattern and magnitude of spatial variation in demography and population growth rate (lambda) is key to understanding the structure and dynamics of natural populations. However, such spatial variation is challenging to quantify. We use>20 years of individual life-history data to quantify small- and large-scale spatial variation in demography and lambda within a single population of red-billed choughs Pyrrhocorax pyrrhocorax on Islay, Scotland. Critically, we demonstrate a major importance of an individual's natal rather than current location in driving observed spatial variation. 2. Breeding success (the number of offspring fledged per breeding attempt) varied among individual chough nest sites but did not vary on a larger spatial scale across Islay. 3. The proportion of fledglings observed to survive to recruiting age varied markedly among individual nest sites and also varied more widely across Islay. Spatial capture-mark-recapture models defined two discrete geographical regions where fledgling survival differed significantly: choughs fledged in region 'BGE' were more likely to survive than choughs fledged in region 'CNSW' as both subadults and adults. 4. The asymptotic lambda attributable to breeding attempts in region BGE exceeded unity, and exceeded that attributable to breeding attempts in region CNSW. Relatively productive and unproductive regions therefore exist within this population. 5. Spatial variation in adult survival was better explained by an individual's natal region than the region where that individual settled to breed. Spatial variation in lambda would consequently have remained undetected had survival been measured across resident breeders rather than across individuals fledged in each region. Furthermore, breeding success was a weak predictor of a nest site's estimated productivity of recruits. 6. We therefore describe marked spatial variation in demography and lambda within a single population of a territorial vertebrate, mediated partly by long-term links between an individual's natal location and its subsequent life-history. Life-long monitoring of individuals of known origin may therefore be necessary to identify accurately subpopulations of intrinsically high and low lambda.     

The phylogenetic position of the Pterosauria within the Archosauromorpha

In recent years the hypothesis that pterosaurs were the major sister-group of dinosaurs and a closely-linked hypothesis that pterosaurs evolved flight from the ground up have gained general acceptance. A cladistic analysis of the Archosauromorpha using characters presented by previous workers results in a single most parsimonious tree with the Pterosauria as the major sister-group of the Dinosauria. However, that sister-group relationship is supported only by a suite of hindlimb characters that are correlated with bipedal digitigrade locomotion in dinosaurs. In pterosaurs the characters have been interpreted as correlates of bipedal cursorial locomotion, arboreal leaping, or involvement of the hindlimb in the wing. The homology of those characters in dinosaurs and pterosaurs cannot be supported. Reanalysis of the data after exclusion of those hindlimb characters results in most parsimonious trees with the Pterosauria as the sister-group of the Erythrosuchidae + Proterochampsidae + Euparkeria + Archosauria, in that order. This sister-group relationship is supported by a diverse assemblage of functionally independent skeletal characters from all regions of the skeleton. The results of the analysis cast doubt on the hypothesis that pterosaurs evolved flight from the ground up.     

Relationship between lordosis and the position of the centre of reaction of the spinal disc

Whenever we stand upright in apparent static equilibrium, we are, in fact, continuously making minor adjustments in order to maintain our balance. For each intervertebral joint, a point must exist at which all moments applied to the joint are continually and dynamically balanced. This point, known as the centre of reaction, is a mathematical invention necessary to perform analyses of spinal motion, but which need not be associated with any real anatomical structure.As the spine flexes and extends, this centre is expected to move; where it moves and the rationale for its motion is worthy of enquiry. In this paper, we propose that the centre of reaction remains confined to the nucleus of the disc, but only if one simple but crucial assumption is made; that the motion of the spine and control of its musculature maintain a minimum and equal stress at each intervertebral joint. This is a simple hypothesis which imposes a very specific relationship between lordosis and the centre of reaction. We investigate this relationship and its consequences on the teaching of lifting.The impossibility of designing experiments adequately to verify this hypothesis prevents in vivo verification, and, therefore, the model's verification must be made through the inferred consequences. For example, the capability of correctly predicting physiological responses of the musculoskeletal system is an indication of the validity of a model; however, this is not universally accepted. In this particular case, additional experimental data are available in the form of the locus of the centre of rotation of a vertebra vis-à-vis its lower neighbour as the spine flexes and extends.It is instructive to compare the predicted locus of the centre of reaction to experimentally determined locus of the centre of rotation; more than just coincidental similarities are found.     

The effect of centre of mass location on sagittal plane moments around the centre of mass in trotting horses

The diagonal limb support pattern at trot provides pitch and roll stability, but little is known about the control of moments about the centre of mass (COM) in horses. Correct COM location is critical in the calculation of pitching moments. The objectives were to determine the effect of COM location on pitching moments in trotting horses and explore how COM location could influence balance.     

深圳近岸养殖牡蛎体内污染物研究

2002年4月25日至8月22日对深圳近岸养殖牡蛎体内的污染物(Cu、Pb、Cd、Zn、Ni、总Cr、总Hg、无机As、石油烃)进行了调查,分析了上述污染物的含量和牡蛎对养殖水体中污染物的浓缩能力,并对其食用质量和养殖海域水体的使用功能进行了评价。结果表明:大亚湾牡蛎体内污染物水平较深圳湾和珠江口低,前者海域养殖牡蛎基本符合要求,只要采用相应的技术进行养殖后的净化处理,该海域养殖的牡蛎可安全食用,后者海域养殖牡蛎体内多项指标超过评价标准,食用质量较差。大亚湾海域可作Ⅰ、Ⅱ类功能使用,深圳湾和珠江口近岸海域作为Ⅲ类功能使用更为合理。牡蛎对污染物浓缩系数依次为Zu>Cu>Cd>Pb>总Cr>Ni>总Hg,其中Zn、Cu、Cd的浓缩系数远大于1000。